Hypoxia is an important factor in luteinization

抄録

This study was carried out to determine whether hypoxia is associated with luteinization. We examined the influence of hypoxia in progesterone (P4) production and protein expression of key steroidogenic factors in P4 biosynthesis; steroidogenic acute regulatory protein (StAR), cytochrome P450 side-chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD) in cultured bovine luteinizing granulosa cells. Granulosa cells were obtained from small antral follicles (≤ 6 mm in diameter). To induce luteinization, the cells were treated for 24 h with insulin (2 µg/ml), forskolin (10 µM) or insulin (2 µg/ml) in combination with forskolin (10 µM). The treatments increased the P4 production in 24 h compared to untreated control. The cells were then incubated in 10% of O₂ as a hypoxic condition or 20% of O₂ as a normoxic condition for 24 h. Interestingly, P4 production by non-luteinizing granulosa cells (control) was not affected by hypoxia, while P4 production by granulosa cells treated with insulin and insulin in combination with forskolin significantly increased under hypoxic condition. Since hypoxia only affected P4 production by luteinizing granulosa cells, hypoxia seems to support but not to induce the luteinization. The protein expression of P4 key steroidogenic factors tended to increase under hypoxic condition with a significant increase only in StAR protein expression in granulosa cells treated with insulin in combination with forskolin. The overall results suggest that hypoxia plays a role during completing luteinization by enhancing P4 production through increasing StAR protein expression in bovine luteinizing granulosa cells.